Why use (void) func() ? (lint beef)

[Rob Lemley]

In <151806 at felix.UUCP> asylvain at felix.UUCP (Alvin E. Sylvain) writes:

>Anyone else out there feel this way?  Any thoughts toward a version
>of lint that's a little less "mother-hen", but still tells you what
>you need to know?  Maybe we could program it with "ignore the following
>problems with the following functions" instructions.

I admit, this has been, and probably will continue to be, a problem with
lint.  A modular, customizable system (ahh Unix) is one answer that we
now have.

On System V Release 3, a great deal of customization can be done with the
current lint.  You must be willing to edit system include files (in
/usr/include) and the lint libraries (usually in /usr/lib).  Of course,
this should be done in a local directory before installing changes in the
system area.

The following type script of a work session illustrates how this can
be accomplished.  Note that lint itself is a shell script which you
may examine at your leisure :-).   The last lint command in the sequence:

	lint -u -n -I. -L. -lc t.c 

uses an undocumented option of lint, the -L option, which specifies search
directories where lint libraries should be found.  Here is a description of the 
options used:

          -u   Suppress complaints about functions and external
               variables used and not defined, or defined and not
               used.  (This option is used because some new functions
               were added to the stdio.h file and not added to the
               lint library file.) 

          -n   Do not check compatibility against either the standard
               or the portable lint library.

          -I.  Search for header files in the current directory
               before /usr/include, etc.

          -L.  This is the undocumented option to lint which creates
               and adds directories to the search list for lint libraries.
               
          -lc  Since the directory search list for lint libraries has now
               been defined, this option tells lint to use the c library
               lint library. (which will be found in the current directory.)


Type script of work session (I have added blank lines before the prompts):

$ cat t.c 

#include <stdio.h>

main()
{
	printf ("hello world\n");
	return 0;
}

$ lint -u t.c 


==============
function returns value which is always ignored
    printf	

$ diff /usr/lib/llib-lc ./llib-lc.c 
381c381
< int	printf(s) char *s; { return (0); }
---
> void	printf(s) char *s; { return ; }

$ diff /usr/include/stdio.h ./stdio.h 
153c153
< extern int 	printf(const char *format, ...);
---
> extern void 	printf(const char *format, ...);
189c189
< 		getw(), pclose(), printf(), fprintf(), sprintf(),
---
> 		getw(), pclose(), fprintf(), sprintf(),
192a193
> extern void	printf();

$ lint -n -v -x -I. llib-lc.c -o c 
"/usr/include/mon.h", line 30: warning: redefinition of:  NULL     

llib-lc.c
==============
(484)  warning: struct/union region never defined

$ lint -u -n -I. -L. -lc t.c 

$

End of work session type script.

The fact that lint is a shell script also lends many possibilities for
local customization.

Another way to alleviate the problem of too much unnecessary output from
lint would be to use some kind of post-processing.  When I was using
the BSD 4.1 system, we had a utility called "error" which would take the
standard and/or error output of cc, cpp, lint, f77, etc. and insert special
comments in the source files at the lines where errors were detected.  The
error command also would read a startup file ($HOME/.ignore or something like
that) where you could specify errors that you wanted to be ignored. This
is where I specified that I didn't want to here about printf(), exit(), etc.

--
-Rob Lemley
 System Consultant, Scanning Software, Intergraph, Huntsville, AL
 ...!uunet!ingr!b15!rcl or b15!rcl at INGR.COM
 205-730-1546